Piston set and compressor thereof

ABSTRACT

This invention discloses a piston set and a compressor thereof. The piston set is disposed in a cylinder of a compressor and comprises a piston and two piston rings. The piston is a rod-shaped structure installed in a ring-shaped groove close to the periphery of both ends of the piston. At least one interference element is formed at the bottom surface of each of the grooves. The two piston rings are installed in the grooves of the piston and being tilted by the interference element respectively. By such arrangements, the invention can improve the air tightness and cooling capacity of the compressor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119 of Taiwan Patent Application No. 101118877, filed on May 25, 2012 in the Taiwan Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piston set and a compressor thereof, more particularly to a piston set and compressor capable of improving the performance of air access of the air compressor.

2. Description of the Related Art

Present industrial air compressors generally compress the volume of air by a mechanical method, so that after the air is compressed to a smaller volume, the original pressure will be increased, and the compressed air can be used for driving machines or for other purposes. In general, the conventional compressors are mainly divided into three types: reciprocating, centrifugal and axial-flow compressors respectively, and most reciprocating compressors perform reciprocating motions of a piston installed in a cylinder of the compressor to achieve the air compression effect. The design of present existing pistons is mainly divided into two types: a design that use Teflon coating and a design that uses Teflon ring respectively.

With reference to FIG. 1 for a schematic view of the conventional Teflon coating method, a piston 10 generally has a interference element 101 disposed at an end of the piston 10, and the interference element 101 is in a close contact with an inner wall of a cylinder, so that when the piston 10 performs the reciprocating motions, the piston 10 can achieve the air compression effect. To avoid wear or damage occurring between the interference element 101 and the inner wall of the cylinder, most manufacturers coat a Teflon layer 102 onto the piston 10 during the manufacture of the piston 10. In general, the interference element 101 and the piston 10 are integrally formed, so that most manufacturers can submerge the piston 10 into a Teflon solution to coat a layer of the Teflon layer 102 on some part of surface of the piston 10 directly. However, only the interference element 101 and the inner wall of the cylinder of the piston 10 are substantially in contact during actual operation, thus wasting production costs and resources. In addition, a small gap is reserved between the piston 10 and the inner wall of the cylinder for the Teflon layer 102, and the gap may have the leakage issue that will cause a drop in cooling capacity.

With reference to FIG. 2 for a conventional way of using the Teflon ring, ring-shaped grooves 103 are generally formed at both ends of the piston 10, and a Teflon ring 11 is sheathed into the respective ring-shaped groove 103 to achieve the same effect as that of the conventional Teflon coating method. However, this design still has the drawbacks on pressure operation and thermal expansion, so that when the piston 10 performs reciprocating motions, the Teflon ring 11 may be cracked, broken or damaged, and the cylinder of the compressor may be worn out or damaged easily in practice.

In view of the aforementioned problems, the inventor of the present invention designed a piston set and a compressor of the present invention to overcome the drawbacks of the prior art and to improve the industrial applications.

SUMMARY OF THE INVENTION

Therefore, it is a primary objective of the present invention to provide a piston set and a compressor thereof to overcome the high cost and the low cooling capacity of the conventional piston sets and compressors.

To achieve the foregoing objective, the present invention provides a piston set installed at a cylinder of a compressor, and the piston set comprises a piston and two piston rings. The piston is a rod-shape structure having a ring-shaped groove concavely formed at a position proximate to the peripheries of both ends of the piston, and at least one interference element disposed at the bottom surface of each groove; and two piston rings, sheathed into the grooves of the piston and being tilted by the interference element respectively, wherein when the piston set performs reciprocal motion within the cylinder, gas enters the cylinder through the piston, so that each of the piston rings extends outwardly from a center axis to make actual contact with a sidewall of the cylinder.

Wherein, each of the interference elements is protruded axially outward from the piston, and the interference element has a bottom-to-top distance falling within a range from 0.15 mm to 0.2 mm.

Wherein, each of the interference element has a cross-section which is a triangular structure, a rectangular structure or an arc structure coupling to two sidewalls of the groove, so that if the cross-section of each of the interference element is the rectangular structure, a sidewall of each of the interference element is coupled to one of the sidewalls of each groove.

Wherein, each piston ring is deformed to form a conical ring-shaped structure during operation, and each piston ring has a first opening and a second opening, and the first opening has a size greater than that of the second opening, and the piston has a bevel formed at an edge of both ends separately, and the piston rings are sheathed from both ends of the piston into the two grooves by using the second openings and the two bevels respectively.

To achieve the aforementioned objective, the present invention further provides a compressor comprising a compressor body and a piston set. Wherein, the compressor body includes a cylinder. The piston set is installed at the cylinder and comprises a piston and two piston rings. The piston is a rod-shape structure having a ring-shaped groove concavely formed at a position proximate to peripheries of both ends of the piston, and at least one interference element protruded outwardly and axially from the bottom surface of each respective groove, and a bottom-to-top distance of each of the interference element falls within a range from 0.05 mm to 0.3 mm; and two piston rings, sheathed into the two grooves of the piston and being tilted by the interference element respectively, wherein when the piston set performs reciprocal motion within the cylinder, gas enters the cylinder through the piston, so that each of the piston rings extends outwardly from a center axis to make actual contact with a sidewall of the cylinder.

Wherein, each of the interference elements has a bottom-to-top distance falling within a range from 0.15 mm to 0.2 mm.

To achieve the aforementioned objective, the present invention further provides a piston set installed at a cylinder of a compressor, and the piston set comprises a piston and a piston ring. The piston is a rod-shape structure having a ring-shaped groove concavely formed at a position proximate to peripheries of both ends of the piston, at least one interference element protruded outwardly and axially from the bottom surface of each respective groove, a chamber axially and concavely formed at a position proximate to at least one part of the periphery of the other end of the piston, and a ring-shaped recess portion axially and concavely formed between the groove and the chamber.

Wherein, the at least one interference element has a bottom-to-top distance falling within a range from 0.15 mm to 0.2 mm.

Wherein, the at least one interference element has a cross-section being a triangular structure, a rectangular structure or an arc structure coupling to two sidewalls of the groove, so that if the cross-section of each of the interference element is the rectangular structure, a sidewall of each of the interference element is coupled one of the sidewalls of each groove.

Wherein, each piston ring is deformed to form a conical ring-shaped structure during operation, and the piston ring has a first opening and a second opening, and the first opening has a size greater than that of the second opening, and the piston has a bevel formed at an edge thereof, and each piston ring is sheathed into two groove from both ends of the piston by using each second opening and each bevel.

In summation, the piston set and the compressor of the present invention have one or more of the following advantages:

(1) The piston set and the compressor of the present invention can assure the piston ring sheathed into the groove to be in a full contact with the inner wall of the cylinder by the at least one interference element and its design with an appropriate size, so as to improve the cooling capacity effectively.

(2) The piston set and the compressor of the present invention can reduce the possibility of cracking, breaking, or damage to the piston ring by the at least one interference element and its design with an appropriate size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a conventional Teflon coating method;

FIG. 2 is a schematic view of a conventional way of using a Teflon ring;

FIG. 3 is a first schematic view of a piston set in accordance with a first preferred embodiment of the present invention;

FIG. 3A is a cross-sectional view along line A-A of FIG. 3.

FIG. 4 is a second schematic view of a piston set in accordance with the first preferred embodiment of the present invention;

FIG. 5 is a schematic view of installing a piston set in accordance with the first preferred embodiment of the present invention;

FIG. 5A is a cross-sectional view along line A-A of FIG. 5.

FIG. 6 is a third schematic view of a piston set in accordance with the first preferred embodiment of the present invention;

FIG. 6A is a cross-sectional view along line A-A of FIG. 6.

FIG. 7 is a fourth schematic view of a piston set in accordance with the first preferred embodiment of the present invention;

FIG. 7A is a cross-sectional view along line A-A of FIG. 7.

FIG. 8 is a fifth schematic view of a piston set in accordance with the first preferred embodiment of the present invention;

FIG. 8A is a cross-sectional view along line A-A of FIG. 8.

FIG. 9 is a sixth schematic view of a piston set in accordance with the first preferred embodiment of the present invention;

FIG. 9A is a cross-sectional view along line A-A of FIG. 9;

FIG. 10 is a schematic view of a piston set in accordance with a second preferred embodiment of the present invention; and

FIG. 10A is a cross-sectional view along line A-A of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The technical characteristics, contents, advantages and effects of the present invention will be apparent with the detailed description of a preferred embodiment accompanied with related drawings as follows. It is noteworthy that the drawings are not necessarily drawn according to the exact proportion or the actual installation since they are provided for the purpose of illustrating the present invention, but not intended for limiting the scope of the invention.

With reference to FIGS. 3 and 4 for the first and second schematic views of a piston set in accordance with a first preferred embodiment of the present invention respectively, the piston set 1 is applied in a compressor 2, and the piston set 1 is installed in a cylinder 21 of the compressor 2 to perform reciprocating motions to achieve the effect of compressing air. The piston set 1 comprises a piston 10 and two piston rings 12. The piston 10 is a rod-shape structure having a ring-shaped groove 104 concavely formed at a position proximate to the periphery of both ends of the piston 10, and a interference element 1041 protruded outwardly from the bottom surface of the groove 104. Two piston rings 12 preferably have a ring body coated with Teflon on the surface of the ring body, and the two piston rings 12 are sheathed into the grooves 104 respectively. When the piston set 1 performs reciprocating motions in the cylinder 21 of the compressor 2, air enters into the cylinder 21 from both end surfaces of the piston 10, so that the piston ring 12 can be stretched open axially outward to have a close contact with a sidewall of the cylinder 21 to achieve the effect of compressing air.

It is noteworthy that the interference element 1041 has a bottom-to-top distance of 0.05-0.3 mm, and preferably 0.15-0.2 mm. When the size of the interference element 1041 is too small, the torque value drops to 0-9 Kg-cm2 after the piston 10 performs reciprocating motions in the cylinder 21 of the compressor 2. Since the torque value is too small, the cooling capacity and the air compression capability of the compressor 2 is reduced. When the size of the interference element 1041 is too large, the torque value is greater than 31 Kg-cm2 after the piston 10 performs reciprocating motions in the cylinder 21 of the compressor 2. Since the cooling capacity and the air compression capability of the compressor 2 simply requires an appropriate amount of torque, therefore an increased torque value will not increase the cooling capacity or the air compression capability of the compressor 2. On the contrary, the friction between the piston ring 12 and the inner wall of the cylinder 21 is increased, so that the compressor 2 requires a greater horsepower to drive the piston set 1 to perform reciprocating motions, and thus wasting energy of the compressor 2 and incurring a possible risk of use. Obviously, appropriate size range and specification of the interference element 1041 can improve the performance of the piston set effectively.

The compressor with the aforementioned design and specification is tested, and the test results are listed in the following Tables 1 and 2.

TABLE 1 Discharge Coefficient of Capacity Temperature Performance Torque BTU/HR ° F. COP ft-lb Rotating Speed: 100 (RPM) Suction Pressure: 45 (psig) Discharge Pressure: 350 (psig) Conventional Teflon Coating 14,136 226 1.59 16.32 Conventional Teflon Ring 9,132 251 1.17 16.05 Design Specification of the 15,220 230 1.62 16.42 Invention (0.15~0.2 mm) Below the Design Specification 12,611 228 1.32 16.21 of the Invention (<0.15 mm) Above the Design Specification 15,230 248 1.63 17.34 of the Invention (>0.2 mm) Rotating Speed: 100 (RPM) Suction Pressure: 35 (psig) Discharge Pressure: 235 (psig) Conventional Teflon Coating 32,664 214 2.12 14.00 Conventional Teflon Ring 24,323 228 1.80 13.96 Design Specification of the 32,986 218 2.22 14.34 Invention (0.15~0.2 mm) Below the Design Specification 29,685 216 2.00 14.21 of the Invention (<0.15 mm) Above the Design Specification 33,087 229 2.25 15.67 of the Invention (>0.2 mm)

TABLE 2 Noise Test (dB) Below Above Design Design Design Rotating Conventional Specification Specification Specification Speed Teflon Conventional of Invention of Invention of Invention (RPM) Coating Teflon Ring (0.15~0.2 mm) (<0.15 mm) (>0.2 mm) 1000 65.2 79.2 64.3 75.0 66.3 1500 69.1 81.7 67.9 78.1 70.1 2000 72.4 83.3 72.7 81.6 73.2 2500 75.1 86 74.3 82.9 76.4 3000 77.3 87.5 76.9 85.0 78.3 3500 78.8 89.7 78.3 87.3 79.3 4000 81.4 91.5 81.0 88.3 82.1 4500 85.0 92.8 85.2 89.4 86.2

In Table 1, if the size of the interference element 1041 is too small (less than 0.15 mm), the coefficients of performance (1.32 and 2.00) will be less than the coefficients of performance (1.62 and 2.22) which is in compliance with the design specification (0.15˜0.2 mm) of the present invention under the same conditions. If the size of the interference element 1041 is too large (greater than 0.2 mm), although the difference between the coefficients of performance (1.63 and 2.25) and the coefficients of performance (1.62 and 2.22) in compliance with the design specification is not large, the difference will cause additional power consumption. In other words, the difference between the torque in compliance with the design specification of the present invention and the torque (17.34, 15.67) of a interference element 1041 that is too-large results in the oversized interference element 1041 increasing the torque and fuel consumption. In addition, the too-large interference element 1041 also affects the temperature, particularly the difference between the discharge temperature (230, 218) in compliance with the design specification of the present invention and the discharge temperature (248, 229) of the interference element 1041 that is too-large shows that a further increase of the size of the interference element 1041 exceeding the design specification of the present invention will not affect the performance in an effective manner, but instead it will affect the power consumption and the temperature. The increased power consumption or temperature will increase the risk of use. In Table 2, the effects of the specification higher or lower than the design specification of the present invention with respect to noise levels are listed. The design specification (with a bottom-to-top distance of the interference element 1041 falling within a range of 0.15˜0.2 mm) of the present invention can achieve a better coefficient of performance and consume less power under the same conditions, so that the design specification (with a bottom-to-top distance of the interference element 1041 falling within a range of 0.15˜0.2 mm) of the present invention is the optimal design specification.

With reference to FIG. 5 for a schematic view of installing a piston set in accordance with the first preferred embodiment of the present invention, the piston ring 12 can be a circular disk with a hole formed at the center of the disk before the installation. After the piston ring 12 is turned in a predetermined direction, the piston ring 12 is deformed to form a conical ring-shaped structure. Now, the piston ring 12 has a first opening 121 and a second opening 122, wherein the first opening 121 has an internal diameter greater than that of the second opening 122. On the other hand, a bevel 105 is disposed on an edge of each end of the piston 10. Now, the two piston rings 12 can be sheathed on an end of the piston 10 by using the second opening 122, and the bevel 105 of the piston 10 can be used to drive the piston ring 12 to move along an inclined plane of the bevel 105 and to be sheathed on a rod body of the piston 10, so as to enter the piston ring 12 into the groove 104 of the piston 10 to complete assembling the piston set 1.

With reference to FIGS. 6 to 9 for schematic views of different implementation modes of an interference element 1041 of a piston 10 in accordance with the present invention respectively, the interference element 1041 of the piston 10 has a cross-section which is substantially a triangular structure, a rectangular structure or an arc structure. If there are plural interference elements 1041, the interference elements 1041 are disposed with an interval apart from one another as shown in FIG. 6. If the cross-section of the interference element 1041 is a rectangular structure, a side of the interference element 1041 is coupled to one of the sidewalls of the groove forming a step formation as shown in FIGS. 7 and 8. If the cross-section of interference element 1041 is an arc structure, the interference element 1041 can be the arc structure coupled to two sidewalls of the groove 104 (as shown in FIG. 9) or the arc structure not coupled to the two sidewalls. In this preferred embodiment, the arc structure coupled to the two sidewalls of the groove 104 is used for the purpose of illustrating the present invention, but the invention is not limited to such arrangement only.

With reference to FIG. 10 for a schematic view of a piston set in accordance with the second preferred embodiment of the present invention, this preferred embodiment is similar to the first preferred embodiment, so that the similar portion will not be repeated. In FIG. 10, the piston set 1 of the present invention is applied in a variable compressor 2. The piston set 1 comprises a piston 10 and a piston ring 12. The piston 10 is a rod-shape structure. The piston 10 has a ring-shaped groove 104 concavely formed at a position proximate to the periphery of an end of the piston 10. The groove 104 has at least one interference element 1041 disposed at the bottom surface of the groove 104. The piston 10 comprises a chamber 106 axially and concavely formed at at least one portion of the piston 10 and proximate to the periphery of the other end of the piston 10, and a ring-shaped recess portion 107 axially and concavely formed at a position between the groove 104 and the chamber 106. The piston ring 12 is sheathed into the groove 104 of the piston 10.

Similarly, the interference element 1041 has a bottom-to-top distance of 0.05˜0.3 mm, preferably 0.15˜0.2 mm. The interference element 1041 has a cross-section being a non-planar shape, such as a triangular structure, a rectangular structure or an arc structure.

In summation of the description above, the present invention has a piston and a piston ring installed separately with respect to each other, and a Teflon layer is coated on an outer surface of the piston ring to effectively reduce the waste caused by the conventional way of submerging the piston into the Teflon solution. In addition, an interference element is further installed in the groove, such that the interference element can overcome the drawback of the piston ring which may be cracked or broken easily by pressure operation or thermal expansion, and the interference element can be installed within an appropriate range to further enhance performance (including the cooling capacity and air compression). 

What is claimed is:
 1. A piston set, installed at a cylinder of a compressor, comprising: a piston, having ring-shaped grooves respectively concavely formed at a position proximate to peripheries of both ends of the piston, and at least one interference element disposed at a bottom surface of each groove; and two piston rings, sheathed into the grooves of the piston and being tilted by the interference element respectively, wherein when the piston set performs reciprocal motion within the cylinder, gas enters the cylinder through the piston, so that each of the piston rings extends outwardly from a center axis to make actual contact with a sidewall of the cylinder.
 2. The piston set of claim 1, wherein each of the interference elements is protruded axially outward from the piston, and has a bottom-to-top distance falling within a range from 0.15 mm to 0.2 mm.
 3. The piston set of claim 1, wherein each of the interference elements has a cross-section of a triangular structure, a rectangular structure or an arc structure coupling to two sidewalls of the groove.
 4. The piston set of claim 3, wherein if the cross-section of each of the interference element is the rectangular structure, a sidewall of each of the interference element is coupled to one of the sidewalls of each groove.
 5. The piston set of claim 1, wherein each of the piston ring is deformed to form a conical ring-shaped structure during a practical operation, and each of the piston ring has a first opening and a second opening, and the first opening has a size greater than that of the second opening, and the piston has a bevel formed at edges of both ends, and the piston rings are sheathed from the ends of the piston into the two grooves by using the second openings and the two bevels respectively.
 6. A compressor, comprising: a compressor body, having a cylinder; and a piston set, installed at the cylinder, comprising: a piston, having ring-shaped grooves respectively concavely formed at a position proximate to peripheries of both ends of the piston, and at least one interference element protruded outwardly and axially from a bottom surface of each respective groove, and a bottom-to-top distance of each of the interference element falls within a range from 0.05 mm to 0.3 mm; and two piston rings, sheathed into the two grooves of the piston and being tilted by the interference element respectively, wherein when the piston set performs reciprocal motion within the cylinder, gas enters the cylinder through the piston, so that each of the piston rings extends outwardly from a center axis to make actual contact with a sidewall of the cylinder.
 7. The compressor of claim 6, wherein each of the interference elements has the bottom-to-top distance falling within a range from 0.15 mm to 0.2 mm.
 8. A piston set, installed at a cylinder of a compressor, comprising: a piston, having ring-shaped grooves respectively concavely formed at a position proximate to peripheries of both ends of the piston, at least one interference element protruded outwardly and axially from a bottom surface of each respective groove, a chamber axially and concavely formed at a position proximate to at least one part of the periphery of the other end of the piston, and a ring-shaped recess portion axially and concavely formed between the groove and the chamber; and a piston ring, sheathed into the groove of the piston and being tilted by the interference element, wherein when the piston set performs reciprocal motion within the cylinder, gas enters the cylinder through the piston, so that the piston ring extends outwardly from a center axis to make actual contact with a sidewall of the cylinder.
 9. The piston set of claim 8, wherein the interference element has a bottom-to-top distance falling within a range from 0.15 mm to 0.2 mm.
 10. The piston set of claim 8, wherein the interference element has a cross-section of a triangular structure, a rectangular structure or an arc structure coupling to two sidewalls of the groove.
 11. The piston set of claim 10, wherein if the cross-section of each of the interference element is the rectangular structure, a sidewall of each interference element is coupled to one of the sidewalls of each groove.
 12. The piston set of claim 8, wherein the piston ring is deformed to form a conical ring-shaped structure during operation, and the piston ring has a first opening and a second opening, and the first opening has a size greater than that of the second opening, and the piston has a bevel formed at an edge thereof, and the piston ring is sheathed into the groove from the end of the piston by using the second opening and the bevel. 